The invention relates to a torque-transmitting apparatus with a fluid-operated torque coupler such as, e.g., a fluid coupling or a hydrodynamic torque converter, with at least one housing that can be connected to a driving shaft of a prime mover. The housing contains at least one impeller pump receiving torque from the housing and a turbine that is connected to the input shaft, such as a transmission shaft, of a power train to be driven. Also, if applicable, the housing contains at least one stator arranged between the pump and the turbine. Further, at least one damper is arranged in the power flow between the turbine and a rotary output element of the device. The damper has an input member constrained to rotate together with the turbine and an output member connected to the rotary output element. The input member and the output member are rotatable relative to each other at least against the opposition of a restoring force furnished by energy-storing devices arranged between them.
Torque-transmitting apparatuses of this kind have been proposed, e.g., in DE-OS 195 14 411. To allow rotational displacement of the input and output members relative to each other, it is customary for torque-transmitting apparatuses of this kind to be equipped with a hub that has a toothed internal profile establishing a positive engagement with the transmission shaft and also a toothed external profile which mates with a further component, normally a further hub that carries the turbine and has a toothed internal profile, with play between the flanks of the mating teeth. When a lockup clutch is added that is activated by an axial control piston, there needs to be a corresponding axial space to allow for the axial travel of the hub containing the two toothed profiles. The manufacture of hubs of this kind is complex and therefore expensive. Furthermore, due to the required axial dimension, longer transmission shafts will be needed. Added to this is the difficulty of connecting bulky hub components with the filigreed construction of the turbine shell. Also, dampers that extend far in the radial direction have a tendency to wobble. If in an attempt to solve these problems, the damper is axially docked to the turbine along two or more perimeters of different radii, this will cause undesirable stresses and frictional losses in the damper.
It is therefore an object of the present invention to improve the design of a torque-transmitting apparatus in a manner that allows a stress-free accommodation of the damper as well as economical and technical improvements in the manufacturing process for torque-transmitting apparatuses of this kind. According to a further object of the invention, the device is to be manufacturable in such a manner that a modular assembly without time-consuming fastening operations can be performed during final assembly. Also required of the torque-transmitting apparatus are the capabilities to transfer torque of high magnitude and to attenuate rotational perturbations over a broad RPM range. Besides, the unit is to meet the objectives that it will minimize wear and prolong the useful life of the overall system of which it is a part.
The invention is embodied in a torque-transmitting apparatus of the kind that has a fluid-operated torque coupler such as a hydrodynamic torque converter or a similar device comprising
at least one housing that can be connected to a driving shaft of a prime mover,
at least one pump that is arranged inside of and driven by the housing,
a turbine that is connected to and drives the input shaft of a power train such as a transmission shaft and also, if applicable,
at least one stator arranged between the pump and the turbine, and further
at least one damper arranged in the torque-flow path between the turbine and a rotary output element of the apparatus, with an input member of the damper being constrained to rotate together with the turbine and an output member of the damper being connected to the rotary output element, the input member and the output member being at least rotatable relative to each other at least against the opposition of the restoring force exerted by energy-storing devices arranged between them.
In accordance with one presently preferred embodiment of the improved torque-transmitting apparatus, the damper at its outside perimeter is directly or indirectly connected to the turbine through a positive rotational constraint. This connection may be free of play relative to coaxial rotational displacements but may allow an axial displacement of the turbine and the input member of the damper relative to each other. For example, the connection may be axially displaceable by means of an axial plug-in connection with the damper rigidly attached to a hub. The problem can further be solved through a torque-transmitting apparatus with a damper whose connection to the turbine shell or turbine, or to the hub, is rotationally fixed both along an inside and outside perimeter, while in the axial direction the connection is fixed only along one perimeter, either on the hub or on the turbine shell, so that axial stresses are relieved by an axial displacement at the axially non-restrained connection.
In accordance with a further inventive concept, there may also be an axially and rotationally fixed connection at the outside perimeter of the damper in which case, in order to prevent stresses in the damper, the inside perimeter of the damper may be designed to be axially displaceable, e.g., in an arrangement where the damper, by means of a positive circumferential coupling such as a toothed profile, engages a complementary profile on the hub. In addition, the profile on the hub may be axially fixed but rotatable on a complementary profile of the turbine hub on which the turbine is seated, with the amount of rotational play designed to be at least equal to the working range, i.e., the effective angular range, of the damper. The play in the form-fitting engagement between the turbine hub and the hub may also be obtained through additional devices such as window-like openings that are distributed over the circumference of the hub and are engaged with angular play by a corresponding series of axially directed projections on the turbine hub.
With particular advantage, the connection between the turbine and the input member of the damper is accomplished through welding processes such as laser welding, impulse welding, or resistance welding, in which case the damper can be centered on the hub by means of a disk-shaped part that holds the energy-storing devices, or on the turbine shell, e.g., by providing the turbine shell with a series of projections that are distributed over the circumference and that may also serve as locating references for the weld.
It is advantageous for the torque-transmitting apparatus to be provided with a lockup clutch arranged in the torque-flow path between the driving shaft and the damper, in which case it has proved to be beneficial if the lockup clutch, by means of friction linings or laminar disks, establishes a positive engagement with a housing surface and transfers the torque to be transmitted directly to the input member of the damper. Thus, when the lockup clutch is engaged, the torque converter is bypassed and the torque to be transmitted is introduced directly into the damper and from there to the rotary output element and subsequently to the transmission shaft. When the lockup clutch is disengaged, the turbine will impart the torque that has been convertedxe2x80x94in most cases amplified through the effect of the statorxe2x80x94to the input member of the damper from where the torque will follow the same path as has been previously described.
The clutch can be engaged and disengaged through an axially moveable control piston that is controlled by an application of pressure. It is advantageous if the control piston defines a plenum chamber which, in the engaged state of the lockup clutch, is essentially sealed tight against the interior space of the housing (except for insignificant flows of pressure medium into the housing that may be provided to cool the friction linings) and is energized by a pressure medium identical to the converter fluid that is admitted through a bore hole, whereby a pressure force is applied to the piston in the axial direction towards the turbine. According to the invention, this axial displacement is compensated by allowing an axial displacement of the axial plug-in connection. Another possibility for controlling the piston is to apply an over pressure to the control piston, in which case the piston will seal off the chamber when the clutch is open; and when the pressure in the chamber is reduced, the piston is pushed to the housing wall by the fluid pressure in the torque converter, thereby causing the lockup clutch to engage.
The control piston can be centered on the transmission shaft, on a hub holding the housing of the torque converter, or on another appropriate part of the apparatus and is preferably provided with sealing means at the interface surfaces to these components for the purpose of sealing the plenum chamber in the same manner as the piston can be sealed at its outside perimeter against the housing.
A further embodiment comprises a form-fitting engagement between the control piston and the housing by means of complementary profiles extending in the axial direction, in which case the axial profile is formed by alternating ridges and grooves in the shape of ring segments that are distributed over a perimeter where, e.g., the ridges of the control piston may engage the grooves in the housing. An advantage of such configuration is the direct engagement of the piston with the housing so that the piston can transmit torque to the friction linings directly and/or through other pressure-transmitting devices, whereby the use of an enlarged friction surface and/or of a larger number of friction surfaces and thus a greater transmission torque is made possible.
For this purpose, there may be one or more carriers of friction linings in the form of annular disks or laminar disks that can carry friction linings in the outer zones of their axially facing surfaces. The friction-lining carriers or laminar disks are axially movable, and the pressure force is applied against a ring-shaped pressure plate that is connected with the housing either directly or indirectly, e.g., welded, riveted or attached to a flange that is, in turn, connected to the housing. For better cooling fluid distribution, the pressure plate can have one or more circles of holes.
It is advantageous to center the friction-lining carrier on the housing. For this purpose, the friction-lining carrier can be provided with lugs that protrude axially towards the housing and are inserted in a shoulder extending in the direction away from the friction-lining carrier.
A further advantageous embodiment renders it possible to configure the piston itself as the lockup clutch or, more precisely, as the friction-lining carrier. For this, the radially outer part of the control piston surface that faces axially towards the housing carries a ring-shaped friction lining that may be provided with an optimized surface finish to achieve better cooling. The piston surface may be bent in the axial direction towards the turbine, so that the piston may rest in form-fitting contact against the housing, which in the respective surface portion is shaped similar to a cone shell.
As already described above, the lockup clutch is connected through one of its components to the input member of the damper. In one embodiment, the connecting part may be the control piston itself in the manner described above, in which case the piston may be connected to lateral parts of the input member by rivets, weld joints or similar means. A further embodiment employs a ring-shaped friction-lining carrier that may form an axial plug-in connection by virtue of an appropriately shaped lateral portion. In this case the friction-lining carrier has a form-fitting engagement with the input member of the damper, e.g., by means of internal teeth at its inside perimeter and, e.g., an axially oriented profile on the lateral part of the input member. The advantages of axial plug-in connections in accordance with the invention are that they compensate for axial displacements and facilitate the manufacturing process by virtue of a modular configuration, because systems of this kind can be built by plug-in assembly without further resort to fastening undertakings such as, e.g., welding or riveting, thus allowing the use of work stations that are not equipped with the respective infrastructure.
Further advantageous embodiments of axial plug-in connections between components of the damper and components of the turbine will be described hereinafter. An advantageous configuration has two components of the two units to be connected meeting each other approximately at a right angle, i.e., in the form of a radially and an axially extending flange, respectively, with the two parts in a form-fitting engagement. In this, it may be advantageous to provide the radially extending flange with external teeth and the axially extending flange with axially oriented teeth.
It may also be advantageous if a radially extending flange-like part has closed cutouts, distributed along a circle of smaller radius than the outside perimeter, that are engaged by axially directed extremities of the axially extending flange-like part.
A preferred embodiment may be a radially oriented flange-like part that, starting at its inside perimeter, follows the shape of the turbine shell outwards in the radial direction and is attached in this portion, e.g., welded or riveted. From there, the flange-like part bends into the radial direction and has a toothed profile along its exterior circumference that is engaged by the lateral part of the input member of the damper. For this purpose, the lateral part at its exterior circumference bends into the axial direction and forms the axially directed flange-like part that carries, e.g., the axially oriented toothed profile.
A further advantageous embodiment may include a flange-like part in the shape of an annular disk that adjoins along its inside perimeter the turbine shell and conforms to the shape of the turbine shell towards the inside in the radial direction, is attached in the shape-conforming portion as described above and then curves into the axial direction. The profile facing away from the turbine shell in axial direction, e.g., a toothed profile, engages in closed recesses distributed over the circumference of a radially directed lateral part and in this manner forms an axial plug-in connection. To form this plug-in connection, it may be necessary for the axially directed toothed profile to pass through the output member before engaging the input member of the damper, given that the output member is interposed axially between the turbine and the input member. For this purpose, the output member has a circular arrangement of elongated holes matching the number of teeth. The angular width of the holes corresponds to the maximum angular displacement of the input and output members relative to each other so that at the same time the elongated holes in combination with the axially directed teeth of the axially oriented flange-like part that is connected to the turbine form at least one stop for the angular displacement of the damper.
In an advantageous arrangement, the axially extending flange-like part can itself be in the form of a hub that carries the turbine, the latter being connected to the hub by, e.g., welding or riveting. The hub carrying the turbine, in turn, can be seated on a further hub that performs the function of the rotary output element and is attached to the transmission shaft. The axially extending flange-like part has a profile established, e.g., by axially oriented teeth that extend into enclosed cutouts corresponding to the number of teeth in the flange whereby an axial plug-in connection is formed. Depending on the configuration of the damper, it may be necessary with this embodiment, too (as described above), to provide in the output member an appropriate arrangement of elongated holes which, in combination with the axially directed profile of the axially oriented flange for the axial plug-in connection, can function as stops for the relative displacement between the input and output members of the damper. The output member, being a radial extension of the hub that is attached to the transmission shaft, may also be configured as a separate flange-like part, in which case the flange needs to be centered on the hub and attached through a rotationally fixed connection.
It can further be advantageous if an annular disk in the form of a radially extending flange-like part with an exterior profile, e.g., an arrangement of external teeth, is centered on the hub that carries the turbine. By attachment means such as, e.g., rivets, the annular disk is rotationally tied to the turbine, and its outward-pointing teeth, mentioned above by way of an example, engage a lateral part that is bent in the axial direction along the interior perimeter and (also by way of example) has a complementary, axially directed toothed profile. In this case, too, a connection is established that constrains rotational but allows translational displacement of the engaged parts relative to each other. The angular displacement of the damper may advantageously be defined by means of a toothed profile with play between the respective tooth flanks of the hub and the annular disk. The outward-facing profile of the hub may also be engaged by the inward-facing profile of the output member, albeit without play at the flanks, in order to secure the output member for rotation with the hub. This has the advantage of saving space in the axial direction of the hub, given that the relative axial displacement occurring between the damper and the turbine as a result of the axial movement of the control piston is already compensated for by the axial plug-in connection.
The axial plug-in connection between the damper and the turbine in different practical variations may be arranged, e.g., at a radial distance beyond the energy-storing devices, at an intermediate radius between the storage devices in the case of at least two damper stages, or inside the radial distance of the storage devices.
Other embodiments of the invention concern the advantageous design of the damper. The damper may be of the single-stage or multi-stage type. A dual-stage damper may be configured in such a way that the damper stages can function in a serial or parallel mode, with the additional possibility of different limits of rotation so that, e.g., in a serial arrangement of the damper stages the relative rotation of one stage is stopped before the other stage, e.g., for the purpose of achieving particular damping characteristics.
In connection with the damper, it is also advantageous to combine different energy-storing devices, e.g., by selecting arc-shaped springs in a radially exterior damper stage, and short, stiff spring elements for use in smaller-diameter areas so that, e.g., a damper characteristic can be achieved that provides a high amount of energy to compensate for both large-amplitude rotational irregularities at low RPM and small-amplitude rotational irregularities at high RPM. In this kind of an arrangement, the arc-shaped springs in the radially exterior area may be pre-bent to their working diameter and are retained radially by a chamber that is formed by at least one lateral part or by other components of the damper or of the torque-transmitting apparatus, e.g., by the wall of the housing. In addition, there may be wear-reducing components such as wear-protection shells interposed between the arc-shaped springs and the chamber, with the characteristic of the arc-shaped spring being determined by all of the aforementioned factors.
It can be advantageous to provide the individual damper stages with displacement properties that depend on the direction from which the torque is introduced. Thus, the damper system may be designed to function in two stages in the xe2x80x9cpullxe2x80x9d mode and in one stage in the xe2x80x9cpushxe2x80x9d mode. In this manner, the damper characteristic may be adapted to the possibility of hard transient peaks in the torque-flow that are introduced from the xe2x80x9cpushxe2x80x9d side, i.e., from the input shaft of the transmission, in which case, e.g., the soft damper stage is bypassed completely and the firm damper stage is effective instantly. The bypass can be accomplished by means of limit stops that block angular displacement against the drive direction in the input and output members of the damper stage that is inactive in the push mode.
It is advantageous to accommodate the storage devices in disk-shaped parts that have dimensionally matched recesses into which the storage devices are fitted and which may at their ends have force-introduction elements facing against the direction of the restoring force. The force-introduction elements retain and thereby compress the storage devices when the input and output members are displaced in relation to each other. The disk-shaped parts forming the input and output members may be arranged in such a manner that either the input or output member is formed by two mutually connected lateral parts, while the other of the two members is formed by a corresponding disk-shaped, flange-like part arranged between the two lateral parts. A further embodiment that brings cost advantages has two disk-shaped parts, one representing a lateral part serving as input member and the other representing a lateral part serving as output member. In two-stage dampers, it can further be cost-effective to use a common disk-shaped part working with both damper stages.
Further in the interest of optimizing cost, the disk-shaped parts may take on additional functions. For example, as mentioned already, one or more disk-shaped parts may form a chamber for the energy storing devices, or they may contain the axial plug-in connection between the damper and the turbine, and/or they may perform other functions.
It is further advantageous for cost-optimization if disk-shaped parts and different other components are made of one piece. Thus, e.g., the output member of the damper together with the rotary output element (e.g., the hub that is arranged on the transmission shaft), or the output member together with the hub that carries the turbine, may be made of one piece.
An advantageous and cost-effective embodiment of means for limiting the extent of angular displacement avoids the need for special stops. For this purpose, a circular arrangement of elongated holes may be provided on at least one disk-shaped part, where the fasteners (e.g., rivets) that are in any case already provided pass through the holes and are held on the opposite side by another disk-shaped part and/or by means of a sheet metal holder. The angular width of the elongated holes is preferably selected so that the extent of relative angular displacement between the input member and the output member is limited by the ends of the elongated holes stopping the shafts of the fasteners.
It is advantageous to provide displacement-limiting stops insofar as a damper or either some or all of the damper stages can be bypassed, so that the damper or the damper stages can be protected from wear. This may apply particularly in the case of wear-prone versions with storage devices that, e.g., contain arc-shaped springs, permit large angular displacements, and/or are exposed to strong shock loads. To guard against premature failure, it is advantageous if initially one damper stage is totally bypassed by means of displacement-limiting stops, while the second stage is either not bypassed at all or only at a later point. When a damper or a damper stage reaches its limit stop, the torque that previously entered into the energy-storing device is transmitted through the stop directly to the output member of the bypassed damper or damper stage. It may also be advantageous to provide different angular displacement limits in the damper device and its damper stages depending on the direction of the torque, i.e., whether the torque works in the pull or push direction, respectively. Thus, it may be advantageous, for example, to provide limit stops in such a manner that a damper stage is entirely bypassed in the costing mode. Likewise, there may be advantages to a configuration in which, e.g., one damper stage works only in the coasting direction while the other stage works only in the pull direction.
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.